<section xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="bind9.library">

<info>

<title>BIND 9 DNS Library Support</title>

</info>

<para>

This version of BIND 9 "exports" its internal libraries so

that they can be used by third-party applications more easily (we

call them "export" libraries in this document). Certain library

functions are altered from specific BIND-only behavior to more generic

behavior when used by other applications; to enable this generic behavior,

the calling program initializes the libraries by calling

<command>isc_lib_register()</command>.

</para>

<para>

In addition to DNS-related APIs that are used within BIND 9, the

libraries provide the following features:

</para>

<itemizedlist>

<listitem>

<para>

The "DNS client" module. This is a higher level API that

provides an interface to name resolution, single DNS transaction

with a particular server, and dynamic update. Regarding name

resolution, it supports advanced features such as DNSSEC validation

and caching. This module supports both synchronous and asynchronous

mode.

</para>

</listitem>

<listitem>

<para>

The "IRS" (Information Retrieval System) library. It provides an

interface to parse the traditional <filename>resolv.conf</filename>

file and more advanced, DNS-specific configuration file for the

rest of this package (see the description for the

<filename>dns.conf</filename> file below).

</para>

</listitem>

<listitem>

<para>

As part of the IRS library, the standard address-name

mapping functions, <command>getaddrinfo()</command> and

<command>getnameinfo()</command>, are provided. They use the

DNSSEC-aware validating resolver backend, and could use other

advanced features of the BIND 9 libraries such as caching. The

<command>getaddrinfo()</command> function resolves both A

and AAAA RRs concurrently when the address family is

unspecified.

</para>

</listitem>

<listitem>

<para>

An experimental framework to support other event

libraries than BIND 9's internal event task system.

</para>

</listitem>

</itemizedlist>

<section>

<info>

<title>Installation</title>

</info>

<screen>

$ <userinput>make install</userinput>

</screen>

<para>

Normal installation of BIND will also install library object

and header files. Root privilege is normally required.

</para>

<para>

To see how to build your own application after the installation, see

<filename>lib/samples/Makefile-postinstall.in</filename>.

</para>

</section>

<section>

<info>

<title>Known Defects/Restrictions</title>

</info>

<itemizedlist>

<listitem>

<para>

The "fixed" RRset order is not (currently) supported in the export

library. If you want to use "fixed" RRset order for, e.g.

<command>named</command> while still building the export library

even without the fixed order support, build them separately:

<screen>

$ <userinput>/configure --enable-fixed-rrset <replaceable>[other flags, but not --enable-exportlib]</replaceable></userinput>

$ <userinput>make</userinput>

$ <userinput>/configure --enable-exportlib <replaceable>[other flags, but not --enable-fixed-rrset]</replaceable></userinput>

$ <userinput>cd lib/export</userinput>

$ <userinput>make</userinput>

</screen>

</para>

</listitem>

<listitem>

<para>

RFC 5011 is not supported in the validating stub resolver of the

export library. In fact, it is not clear whether it should: trust

anchors would be a system-wide configuration which would be managed

by an administrator, while the stub resolver will be used by

ordinary applications run by a normal user.

</para>

</listitem>

<listitem>

<para>

Not all common <filename>/etc/resolv.conf</filename> options are

supported in the IRS library. The only available options in this

version are <command>debug</command> and <command>ndots</command>.

</para>

</listitem>

</itemizedlist>

</section>

<section>

<info>

<title>The dns.conf File</title>

</info>

<para>

The IRS library supports an "advanced" configuration file related to

the DNS library for configuration parameters that would be beyond the

capability of the <filename>resolv.conf</filename> file.

Specifically, it is intended to provide DNSSEC related configuration

parameters. By default the path to this configuration file is

<filename>/etc/dns.conf</filename>. This module is very experimental

and the configuration syntax or library interfaces may change in

future versions. Currently, only the <command>trusted-keys</command>

statement is supported, whose syntax is the same as the same

statement in <filename>named.conf</filename>. (See

<xref linkend="trusted-keys"/> for details.)

</para>

</section>

<section>

<info>

<title>Sample Applications</title>

</info>

<para>

Some sample application programs using this API are provided for

reference. The following is a brief description of these

applications.

</para>

<section>

<info>

<title>sample: a simple stub resolver utility</title>

</info>

<para>

Sends a query of a given name (of a given optional RR type) to a

specified recursive server and prints the result as a list of RRs.

It can also act as a validating stub resolver if a trust anchor is

given via a set of command line options.

</para>

<para>

Usage: sample [options] server_address hostname

</para>

<para>

Options and Arguments:

</para>

<variablelist>

<varlistentry>

<term>-t RRtype</term>

<listitem>

<para>

specify the RR type of the query. The default is the A RR.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>[-a algorithm] [-e] -k keyname -K keystring</term>

<listitem>

<para>

specify a command-line DNS key to validate the answer. For

example, to specify the following DNSKEY of example.com:

<literallayout>

example.com. 3600 IN DNSKEY 257 3 5 xxx

</literallayout>

specify the options as follows:

<screen>

<userinput>-e -k example.com -K "xxx"</userinput>

</screen>

-e means that this key is a zone's "key signing key" (also known

as "secure entry point").

When -a is omitted rsasha1 will be used by default.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-s domain:alt_server_address</term>

<listitem>

<para>

specify a separate recursive server address for the specific

"domain". Example: -s example.com:2001:db8::1234

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>server_address</term>

<listitem>

<para>

an IP(v4/v6) address of the recursive server to which queries

are sent.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>hostname</term>

<listitem>

<para>

the domain name for the query

</para>

</listitem>

</varlistentry>

</variablelist>

</section>

<section>

<info>

<title>sample-async: a simple stub resolver, working asynchronously</title>

</info>

<para>

Similar to "sample", but accepts a list

of (query) domain names as a separate file and resolves the names

asynchronously.</para>

<para>

Usage: sample-async [-s server_address] [-t RR_type] input_file</para>

<para>

Options and Arguments:

</para>

<variablelist>

<varlistentry>

<term>-s server_address</term>

<listitem>

an IPv4 address of the recursive server to which queries are sent.

(IPv6 addresses are not supported in this implementation)

</listitem>

</varlistentry>

<varlistentry>

<term>-t RR_type</term>

<listitem>

specify the RR type of the queries. The default is the A

RR.

</listitem>

</varlistentry>

<varlistentry>

<term>input_file</term>

<listitem>

a list of domain names to be resolved. each line consists of a

single domain name. Example:

<literallayout>

www.example.com

mx.example.net

ns.xxx.example

</literallayout>

</listitem>

</varlistentry>

</variablelist>

</section>

<section>

<info>

<title>sample-request: a simple DNS transaction client</title>

</info>

<para>

Sends a query to a specified server, and prints the response with

minimal processing. It doesn't act as a "stub resolver": it stops

the processing once it gets any response from the server, whether

it's a referral or an alias (CNAME or DNAME) that would require

further queries to get the ultimate answer. In other words, this

utility acts as a very simplified <command>dig</command>.

</para>

<para>

Usage: sample-request [-t RRtype] server_address hostname

</para>

<para>

Options and Arguments:

</para>

<variablelist>

<varlistentry>

<term>-t RRtype</term>

<listitem>

<para>

specify the RR type of the queries. The default is the A RR.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>server_address</term>

<listitem>

<para>

an IP(v4/v6) address of the recursive server to which

the query is sent.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>hostname</term>

<listitem>

<para>

the domain name for the query

</para>

</listitem>

</varlistentry>

</variablelist>

</section>

<section>

<info>

<title>sample-gai: getaddrinfo() and getnameinfo() test code</title>

</info>

<para>

This is a test program to check <command>getaddrinfo()</command> and

<command>getnameinfo()</command> behavior. It takes a host name as an

argument, calls <command>getaddrinfo()</command> with the given host

name, and calls <command>getnameinfo()</command> with the resulting

IP addresses returned by <command>getaddrinfo()</command>. If the

dns.conf file exists and defines a trust anchor, the underlying

resolver will act as a validating resolver, and

<command>getaddrinfo()</command>/<command>getnameinfo()</command>

will fail with an EAI_INSECUREDATA error when DNSSEC validation

fails.

</para>

<para>

Usage: sample-gai hostname

</para>

</section>

<section>

<info>

<title>sample-update: a simple dynamic update client program</title>

</info>

<para>

Accepts a single update command as a command-line argument, sends

an update request message to the authoritative server, and shows

the response from the server. In other words, this is a simplified

<command>nsupdate</command>.

</para>

<para>

Usage: sample-update [options] (add|delete) "update data"

</para>

<para>

Options and Arguments:

</para>

<variablelist>

<varlistentry>

<term>-a auth_server</term>

<listitem>

<para>

An IP address of the authoritative server that has authority

for the zone containing the update name. This should

normally be the primary authoritative server that accepts

dynamic updates. It can also be a secondary server that is

configured to forward update requests to the primary server.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-k keyfile</term>

<listitem>

<para>

A TSIG key file to secure the update transaction. The

keyfile format is the same as that for the nsupdate utility.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-p prerequisite</term>

<listitem>

<para>

A prerequisite for the update (only one prerequisite can be

specified). The prerequisite format is the same as that is

accepted by the nsupdate utility.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-r recursive_server</term>

<listitem>

<para>

An IP address of a recursive server that this utility will

use. A recursive server may be necessary to identify the

authoritative server address to which the update request is

sent.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-z zonename</term>

<listitem>

<para>

The domain name of the zone that contains

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>(add|delete)</term>

<listitem>

<para>

Specify the type of update operation. Either "add" or

"delete" must be specified.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>"update data"</term>

<listitem>

<para>

Specify the data to be updated. A typical example of the

data would look like "name TTL RRtype RDATA".

</para>

</listitem>

</varlistentry>

</variablelist>

<note>

<simpara>

In practice, either -a or -r must be specified. Others can be

optional; the underlying library routine tries to identify the

appropriate server and the zone name for the update.

</simpara>

</note>

<para>

Examples: assuming the primary authoritative server of the

dynamic.example.com zone has an IPv6 address 2001:db8::1234,

</para>

<screen>

$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key add "foo.dynamic.example.com 30 IN A 192.168.2.1"</userinput></screen>

<para>

adds an A RR for foo.dynamic.example.com using the given key.

</para>

<screen>

$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com 30 IN A"</userinput></screen>

<para>

removes all A RRs for foo.dynamic.example.com using the given key.

</para>

<screen>

$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com"</userinput></screen>

<para>

removes all RRs for foo.dynamic.example.com using the given key.

</para>

</section>

<section>

<info>

<title>nsprobe: domain/name server checker in terms of RFC 4074</title>

</info>

<para>

Checks a set of domains to see the name servers of the domains

behave correctly in terms of RFC 4074. This is included in the set

of sample programs to show how the export library can be used in a

DNS-related application.

</para>

<para>

Usage: nsprobe [-d] [-v [-v...]] [-c cache_address] [input_file]

</para>

<para>

Options

</para>

<variablelist>

<varlistentry>

<term>-d</term>

<listitem>

<para>

Run in "debug" mode. With this option nsprobe will dump

every RRs it receives.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-v</term>

<listitem>

<para>

Increase verbosity of other normal log messages. This can be

specified multiple times.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-c cache_address</term>

<listitem>

<para>

Specify an IP address of a recursive (caching) name server.

nsprobe uses this server to get the NS RRset of each domain

and the A and/or AAAA RRsets for the name servers. The

default value is 127.0.0.1.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>input_file</term>

<listitem>

<para>

A file name containing a list of domain (zone) names to be

probed. when omitted the standard input will be used. Each

line of the input file specifies a single domain name such as

"example.com". In general this domain name must be the apex

name of some DNS zone (unlike normal "host names" such as

"www.example.com"). nsprobe first identifies the NS RRsets

for the given domain name, and sends A and AAAA queries to

these servers for some "widely used" names under the zone;

specifically, adding "www" and "ftp" to the zone name.

</para>

</listitem>

</varlistentry>

</variablelist>

</section>

</section>

<section>

<info>

<title>Library References</title>

</info>

<para>

As of this writing, there is no formal "manual" for the libraries,

except this document, header files (some of which provide pretty

detailed explanations), and sample application programs.

</para>

</section>

</section>